This could also be translated as "They will fill in every low place in the road." When people prepare the road for an important person who is coming, they fill in the low places with dirt so that the road will be level. This is part of the metaphor started in the previous verse. (See: [[rc://en/ta/man/translate/figs-metaphor]])
This could also be translated as "They will level every mountain and hill" or "They will remove every high place in the the road." (See: [[rc://en/ta/man/translate/figs-metaphor]])